Insulating tube



April 24, 1928.

P. A. HUNERMANN INSULATING' TUBE Filed Sept. 28. 1926 'Patented Apr. 24, 1928.`

UNlTED TES MNM-5- PETER ADOLF HNERMANN, 0F`BERLINJWEISSENSEEy GERMANY, ASSIGNORTO THE FIRM JAROSLAWS ERSTE GLIMMERWARENEVABRIK IN BERLN, 0F vi3'.fk'llflil wnrssnnsnn, GERMANY.

XN'SU'LATING TUBE.

- AppIication filed September 28, Q26, Serial No. 138,245, and in Germany may 14, i925.

My invention refers to insulating tubes of the kind which are formed by winding webs of paper or other insulating material coated with a binder and Lhaving a considerable Width around a rotating mandrel. In the manufactureof such tubes their length is limited by the width of the webs available lfor this purpose. lf it is desired to manufacture long tubes, several such webs must be wound around the mandrel in juxtaposition and the' diiiiculty arises of connecting the abutting edges ofthe wound-up webs and adjoining cutting edges., However, insu.-

lators manufactured in this manner are still deficient in that the joint thus. obtained between the two wound-up webs has the form of a' plain annular gap which although being filled up with the lacquer or other insulating coating covering the paper still possesses an insulating capacity which is inferior to that of the other portions of the insulator, the cellulose of the paper being far superior in this respect to all lacquers, resins or other insulating coatings.

In the insulator according to the present invention the diiference of insulating capacity is altogether avoided by forming the two abutting sections in such manner that their engaging ends have the form of concentric rings of conical sect-ion and stepped surface, whereby the gap which separates the two sections has a cross lsection bordered by a zigzag line and is closed in radial direction by the adjoining layers of paper so that the.

inferior insulating capacity at thejoints as compared with the total radial section is so insignificantv as to be altogether negligible.

Even if ythe several adjoining layers are staggered only so little that the joints of adjoining layers communicate with each other,

much as the path odered to the current is greatly lengthened.

However, in a preferred embodiment of this invention the several layers are staggered to such an extent that the dielectric resistance of the zigzag path formed by the joint is great enough to withstand t-he pressure necessary for a radial passage of curv rent across each layer. A staggered displacement of 5 mms. between adjoining layers will sudice in ordinary cases.

lin order to produce insulators such as above described, l prefer leading the two adjoining webs with their marginal portions overlapping each other, as above described, and at the same time lf cause the cutter severing these portions of the two webs to be laterally displaced during the cutting operation in such manner that the overlapping portions are cut through in an undulating lino whereby the engaging ends of the two abutting sections are formed with stepped concentric rings of conical section.

fn the drawings alixed to this specification and forming part thereof an insulator according to the present invention and the manner of making same is illustrated diagrammatically by way of example.

ln the ydrawings Fig. l is an axial section of the tube, showing the abutting ends of the two sections of the tube with the zigzagline bordering the cross sections of their ends.

Fig. 2 is a perspectiveend view of one of the two sections, and

Fig. 3 is an elevation, partly in axial seotion, of the mandrel, the two overlapping webs and the cutter severingthem during manufacture.

Fig. 4f is a diagram showing means for displacing the cutter.

In the drawings l is the mandrel supported and set rotating in any suitable manner and 2 and 3 are the two webs which shall be wound upon the mandrel. As shown in the drawings the marginal portions of the two webs overlap each other and 'directly before being wound up are cut through by means of a cutter 4 of some well known kind which is mounted ou a threaded spindle 5 running in threaded bearings 6 for lateral displacement in both directions in parallel to the mandrel, whereby the cutter is displaced for instance the insulating capacity will still be -far sue 5 mms. to the left during one revolution of perior to that of a plain annular joint inas? the mandrel. After the cutter has been thus displaced several times in one direction, its movement is reversed, the cutter being now displaced toithe right, and so forth until the insulator is finished. If it is shown for instance that the cutter is capable of travelling 50 mms. to the left'and50 mms. to the right -from its normal position, a reversal of the movement of the cutter will take place only after windings and joints having the same radial position will occur only after 20 windings so that the insulating capacity is not in the least impaired.

Fig. 1 sliows the zigzag line 7 bordering the cross sections of the butting ends of the two wound-up webs and Fig. 2 shows the concentric rings 8 of'co-nical section which Y are thus interlocked.

ing ofclosely adjoining layers of insulating material, the engaging ends of said sections cal section.

2. nsulating tube consisting of a spirally wound sheet of insulating material and com'- prising two adjoining sections, each consisting of closely adjoininglayers of insulating material, the engaging ends of said sections having conical surfaces stepped in spirals.

3. Insulating tube consisting of a spirally wound sheet of insulating material and colnprising two adjoinin ing ends of said sections having axial sections bordered by a zigzag line.

4. Insulating tube consisting of a spirally sections, the engagwound, sheet of insulating material and com- Y prising two adjoining sections, the engaging PETER, ADOLF HNERMANN.

In testimony whereof I aiix my signature. having the form of concentric rmgs of coni- 

